1. Field of the Invention
The present invention relates to compositions which are useful for cleaning and lubricating air conditioning systems. In one of its more particular aspects, this invention relates to such compositions which are particularly useful in cleaning and lubricating automotive air conditioners. Still more particularly, the chemical composition taught by this invention is useful in servicing an automotive air conditioning system as part of a change over of the system from F-12 to a newer none ozone-depleting refrigerant, such as F-134.
2. Related Technology
Concern that chlorofluorocarbons may cause stratospheric ozone depletion has mandated the replacement of chlorofluorocarbons (i.e., such as refrigerant F-12) by refrigerants which are not ozone depleters. For this reason, chlorofluorocarbon refrigerants have largely been replaced in newer automobiles by refrigerants which are hydrofluorocarbons (i.e., such as F-134). This change in refrigerants for automotive use has resulted in the need for compositions, for example, cleaners and lubricants for air conditioning systems, which are compatible with hydrofluorocarbons. This is especially the case when an older automotive air conditioning system that was designed to use F-12, is changed over to the newer F-134 refrigerant. Mineral-based lubricants, that were previously used in F-12 air conditioning systems, while compatible with chlorofluorocarbons, have been found to be incompatible with hydrofluorocarbons, such as F-134. Therefore, lubricants other than the typical mineral-based lubricants must now be provided for use in refrigeration systems employing hydrofluorocarbons.
When an older automotive air conditioning system is serviced at the present time, F-12 cannot be placed back into the system because it is prohibited by Federal law to do so. The system must be converted to use the newer F-134 type of refrigerants. In this situation, it is common for several major components of the system to be changed. For example, the condenser coil (i.e., heat exchanger) may be replaced with a larger one that is better suited to the user of R-134. Further, the evaporator coil and thermal expansion valve, or liquid refrigerant metering orifice, for example) may also be replaced for the same reason. The receiver/drier of the system is almost always replaced with a new one any time an automotive air conditioning system is opened up for service. Finally, the compressor of the air conditioning system may or may not be replaced with a newer and larger compressor. Usually, the refrigerant lines of the system are not replaced if they are in good condition.
In the above-described context of service and replacement of components of an older automotive air conditioning system, the choice of lubricant used in the system in fact may be critical to successful operation of the air conditioning. Particularly, if the old compressor is retained, the mineral lubricating oil must be drained from the compressor, and new oil which is compatible with the new refrigerant and the old compressor must be supplied into the system.
Such lubricating compositions which are used in automotive air conditioning systems must not only clean and lubricate moving parts, but must also cycle repeatedly through an automotive air conditioning system, without breaking down under conditions of high temperatures and pressures. The lubricants must also be capable of flowing through the system at low temperatures.
It is further required that a cleaning and lubricating composition which can be used as part of the service procedure as outlined above to convert an older automotive air conditioning system to R-134 type of refrigerant, or which may be used in the service of a system designed originally to use the R-134 type of refrigerants, must provide cleaning, antioxidant, and anti-wear properties, and must also withstand extreme pressures. It is essential that the composition not only be compatible with the refrigerant, but that it also provide excellent protection from wear and corrosion of ferrous, aluminum, and bronze parts of the air conditioning system. It must not deteriorate seals, closures, and flexible hoses of the system.
To the present time, no such cleaning and lubricant composition has been available for use in the automotive market. Consequently, it is common practice for automotive air conditioning systems that are being serviced to have components that are returned to service even though they may harbor remnants of the old mineral oil lubricant, as well as possibly debris from a damaged compressor, for example. Alternatively, it is common for many components of an automotive air conditioning system to be replaced when they may be in serviceable condition except for concerns about not being able to clean these components adequately.
It is accordingly an object of the present invention to provide compositions for cleaning and lubricating automotive air conditioning systems.
It is another object of the present invention to provide such compositions which are compatible with hydrofluorocarbon refrigerants.
Accordingly, the present invention, according to one aspect, provides an automotive air conditioner system cleaning and lubricating composition comprising: a mixture of tetrafluoroethane, 2,3-dihydroperfluoropentane, tricresyl phosphate, and a polyol ester.
Further, and in general, it has been found that compositions for cleaning and lubricating automotive air conditioning systems which do not deplete ozone can be formulated using a mixture of hydrofluorocarbons. The mixture of hydrofluorocarbons is combined with polyol ester lubricants and extreme-pressure additives. A typical formulation consists of a mixture of tetrafluoroethane (Freon R-134a), 2,3-dihydroperfluoropentane, a polyol ester, and tricresyl phosphate.
In this mixture the polyol ester lubricant and tricresyl phosphate extreme-pressure additive together comprise about 1% to 10% by weight of the overall mixture, whereas the tetrafluoroethane makes up from about 60% to about 70% of the composition, and the 2,3-dihydroperfluoropentane comprises about 30% by weight of the overall mixture.
In the solvent mixture of tetrafluoroethane and 2,3-dihydroperfluoropentane, which makes up about 90% of the mixture, the tetrafluoroethane comprises about ⅔rd to about {fraction (7/10)}th of the solvents, and the 2,3-dihydroperfluoropentane comprises about ⅓rd to about {fraction (3/10)}th of the solvent mixture.
The cleaning and lubricating compositions of the present invention are effective in removing traces of chlorofluorocarbons, as well as oils, which may be present in automotive air conditioning systems because of the previous use of chlorofluorocarbons and mineral oil lubricants. The compositions of the present invention are effective in both cleaning and lubricating automotive air conditioner systems. They are compatible with Freon R-12, Freon R134a, other hydrofluorocarbons, mineral oils, alkyl benzenes, and polyalkylene glycols. The lubricant constituent provides excellent wear protection and anti-corrosion for various metal parts, including aluminum, iron, and bronze parts. They provide very good low temperature fluidity as well as high temperature film strength, which assures internal lubrication at both low and high ambient conditions. In addition, they are compatible with seal and hose materials and are unaffected by residual chlorine and other contaminants that may be in the automotive air conditioning system.
Other objects and advantages of the present invention will become apparent from the following detailed disclosure and description.